DIAGNOSTICS FOR EMISSION CONTROL SYSTEM MALFUNCTION ON THREE-WAY

CATALYST-EQUIPPED VEHICLES

Final Report

Prepared for:

CALIFORNIA AIR RESOURCES BOARD El Monte, California

Prepared by:

ENERGY AND ENVIRONMENTAL ANALYSIS, INC. 1655 North Fort Myer Drive Arlington, Virginia 22209

November 1985

PHASE I

TABLE OF CONTENTS

Page 1. INTRODUCTION •••••••••••••••••••••••••••••••••••••••••••••••••• 1-1

2. REVIEW OF MANUFACTURER RECOMMENDED DIAGNOSTIC PROCEDURES•••••• 2-1

2.1 Introduction············································· 2-1

2.2 Secondary Air Systems···································· 2-5

2.3 EGR Systems · · • · · • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 2-9

2. 4 Fuel Systems · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 2-13

2.5 Catalyst System·········································· 2-23

SURVEY OF FIELD MECHANICS .•.•••.••.••.•••••.•••.•••.•••••••••• 3-13.

3.1 Introduction···················•······••·•••••••••••••••• 3-1

3.2 Mechanics' Experience···································· 3-2

3.3 Approach to Diagnostics 3-5

3.4 System Specific Details 3-7

Additional Comments · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 3-8

4. DESIGN OF GENERALIZED DIAGNOSTIC METHODS ••..•••..••.•••••••••. 4-1

4 .1 Overview · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 4-1

4.2 Diagnostic Procedures Requirements ·•••••••••••·••••·•·••• 4-2

4.3 Generalized Test Procedures······························ 4-6

5. POTENTIAL GARB ACTIONS TO INCREASE DIAGNOSTICS EFFECTIVENESS • • · · · • • • • • · · · • • · • • · • • · · • • • • • · • • • • • • · • • • • • • • • • • • • • 5-1

APPENDIX A

APPENDIX B

LIST OF TABLES

Page

2-1 Key to Manufacturer-Recommended Diagnosis Procedures········ 2-3

2-2 Possible Causes of Emissions Test Failures·················· 2-6

2-3 Diagnosis Procedures for Air Injection Systems·············· 2-7

2-4 Diagnosis of Toyota Closed-Loop Air Injection•·············· 2-10

2-5 Diagnosis of EGR Systems···································· 2-11

2-6 Diagnosis Procedures for Open-Loop Carburetors·············· 2-14

2-7A Diagnosis Procedures for Closed-Loop Carburetor············· 2-16

2-7B Diagnosis Procedures for Chrysler Closed-Loop Carburetor2-18

2-8 Diagnosis Procedures for Closed-Loop Fuel Injection········· 2-20

2-9 Diagnosis Procedures for Closed-Loop EFI Systems············ 2-21

2-10 Diagnosis of Catalyst System································ 2-24

3-1 Experience of Mechanics Surveyed···························· 3-3

4-1 Emissions Failures Due to Intentional Malperformance 4-3

4-10 Diagnostic Method for Electronically Fuel-Injected

4-12 Preliminary Recommendations for Catalyst System

4-2 Emissions Failures Due to Intentional Malperformance •••••••• 4-4

4-3 Basic Requirements for Diagnostic Method···················· 4-8

4-4 Secondary Air Systems With Air Pump························· 4-9

4-5 Diagnosis of EGR Systems···································· 4-13

4-6 Closed-Loop System Performance Check and Oxygen Sensor Check················································ 4-16

4-7 Test Results From System Performance Check 4-17

4-8 Diagnostic Method for Feedback Carburetors 4-19

4-9 Diagnostic Method for Bosch K-Jetronic Fuel System·········· 4-21

Systems • · · · · · · · · · · • • • · • • · • · · · • · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · 4-23

4-11 Trouble Codes for C-4 On-Board Diagnostics·················· 4-24

Diagnostic · · · · · · · • · · • · · · · · · · · · · · · · · · · · • • · · • • • • • • • · • · · · · · · · · • 4-26

LIST OF FIGURES

Page

2-1 Comparison of Multiple Indicators of Catalyst Poisoning•····· 2-26

4-1 Schematic of Secondary Air System···························· 4-11

4-2 Schematic of EGR Systems ·•••••••••••••••••••••••••·•••••·•••• 4-15

4-3 Schematic of Bosch Mechanical Fuel-Injection System•········· 4-22

1. INTRODUCTION

Emission standards for model year 1980 and later cars have required many

auto-manufacturers to employ sophisticated emission control systems with

"three-way" catalysts. Such catalysts require careful control of engine

operating parameters to obtain optimum emission control. Each manufac

turer has developed alternative emission control systems that, while

often similar in concept, are substantially different in design and

construction. Many of these emission control systems utilize electronic

controls that link the various individual components together to operate

as an integrated system. The resulting variety of alternative systems

has strained the ability of the service sector to diagnose and repair

malfunctions, as they have made traditional trial and error methods of

analyzing engine and emission control system malfunctions virtually

impossible. To aid mechanics diagnose such systems, manufacturers have

developed separate specialized diagnostic equipment and testing procedures,

but the equipment varies by individual vehicle type and model year.

Since it appears questionable whether the service industry can rapidly

adapt to this changing environment, the California Air Resources Board

(CARB) has contracted EEA to: (1) review current manufacturer-recommended

diagnostic procedures for identifying emission control malfunctions; (2)

survey diagnostic techniques used in the field; and (3) develop and

recommend a set of standardized diagnostic procedures for use by service

industry mechanics. The scope of the effort was restricted to three-way

catalyst cars, while diagnosis of malperformance was required for:

• The EGR system

• The Secondary air system

• The fuel system

• The catalyst

1-1

This report documents EEA's efforts under the first Phase of this contract

and presents generalized diagnostic methods applicable to a wide variety

of cars. The validation of these methods is performed in Phase II of

the contract, and is documented in a companion report.

Section 2 of this report provides our detailed review of current manufac

turer recommended methods for diagnosing malfunctions in the emission

control system. These methods provide a baseline from which the

generalized diagnostic procedures were developed. The CARB had provided

a list of 17 cars as a sample representing a broad spectrum of emission

control systems. EEA obtained repair manuals for 16 of these vehicles

(one repair manual was prohibitively expensive and the recommended methods

were almost identical to those for several other cars in the sample) and

organized the manufacturer recommended methods for diagnosis into groups

featuring common or similar technological characteristics. The data is

presented in a series of tables that are intended to exhibit the similari

ties and differences in manufacturer recommended test methods.

Section 3 of the report presents a summary of the results of the survey

of field mechanics conducted by J.D. Power. The survey was performed to

identify both the procedures used and problems faced by mechanics in the

field when diagnosing three-way catalyst cars with emission control system

malperformances. The sample of mechanics was small and the survey should

not be viewed as a formal statistical one, but as one where the results

can provide some insight into mechanics' concerns. The purpose of the

survey was to focus the generalized diagnostic procedures developed in

this effort towards mechanics' needs. The detailed results of the survey

have already been presented to the CARB separately; only a summary of

the results are provided in this report.

Section 4 details the generalized procedure developed by EEA as well as

the rationale employed in the development of the generalized procedures.

1-2

These procedures are based on the fact that, although 3-way catalyst

emission control systems vary widely in mechanical details, they are

based on some fundamentally similar concepts. The diagnostic methods

presented here are not intended to replace the manufacturers diagnostics,

but, rather, to supplement them by providing the mechanic with a few

simple tests, requiring no special tools, that can diagnose those emission

control system malperformances having potentially large impact on emis

sions. Moreover, the methods presented here are not in a form that can

be given directly to mechanics, but provide enough information for the

development of a service manual.

EEA also recognizes that diagnostic methods based on existing emission

control systems alone will not solve all of the mechanics problems in

diagnosing malperformances. Accordingly, in Section 5 we suggest other

remedial measures that can be independently pursued by the GARB to aid

mechanics.

1-3

2. REVIEW OF MANUFACTURER RECOMMENDED DIAGNOSTIC PROCEDURES

2.1 INTRODUCTION

As a first step towards the development of standardized diagnostic proce

dures for three-way catalyst equipped cars, a detailed review of manufac

turer recommended diagnostic procedures was undertaken by EEA. The CARE

had established a reference list of 17 vehicles representing the spectrum

of emission control technology utilized in current vehicles. The survey

of manufacturer recommended procedures was based on the methods recommended

in their repair manuals for the 17 vehicles specified by the CARE. In

this section of the report, EEA has organized the emission control tech

nologies employed in the reference list of cars into groups that employ

similar emission control strategies and reviewed the diagnostics recommended

for each group. The results of the review are presented in a tabular

format, where the essential features of each manufacturers' diagnostic

procedure are highlighted.

The review was limited to diagnostics of malperformances in the:

• EGR system

• Secondary air system

• Fuel system

• Catalyst system

In addition, EEA has reviewed only those parts of the fuel system that

are specially designed for emission control in conjunction with three

way catalysts. This is because many of the components of the fuel system

relate only to fuel delivery, not to emission control. The study

methodology assumes that the procedures for dealing with malfunctions

for such components are widely understood as they have been available

for many years. Hence, diagnostics and repair methods for malfunctions

2-1

such as carburetor idle-mixture, sticky choke or binding throttle linkages

are not the subjects of this study although any of these malfunctions

can induce significant increases in emissions. Since the study of diag

nostic methods and repair of these malfunctions would result in essentially

duplicating BAR developed diagnostics, the study limitations were chosen

to maximize our efforts to develop diagnostics for new three-way catalyst

related emission control technology.

Table 2-1 presents an overview of the systems employed in the reference

list of vehicles. (One 1980 GM car was eliminated from study because it

used an early version the GM C-3 emission control system. This version

was subsequently updated in the 1981 and later model year cars which are

analyzed in this report.) Note that four of the cars -- Volvo, Audi, VW

and Peugeot --utilize the Bosch Continuous Injection System (CIS) with

the three-way catalyst. The Bosch CIS is identical in design and opera

tion in each of the four vehicles and diagnostic procedures for such

vehicles are grouped into a single table.

Table 2-1 also shows the current status of manufacturer's guidance to

mechanics for diagnostics on an emissions failure. Surprisingly, the GM

Chevette shop manual was the only one to provide mechanics a listing of

possible causes of emissions failures for HC, CO, and NO. Other manuals X

such as the one for Toyota and Ford provide some guidance on specific

malperformances or warnings on secondary air division, but most manuals

provide no guidance whatsoever to mechanics on potential causes for emis

sions failures. All manuals provide diagnostics for driveability related

defects -- e.g., surge, stumble, failure to start, backfire -- which

may, in some cases, lead to correction of an emissions related failure.

The Fiat manual was the exception as it provided no diagnostic methods

at all. It is likely that EEA obtained the wrong manual, but since Fiat

is currently closing down its North American operations, we were unable

to obtain further literature from Fiat.

2-2

TABLE 2-1

KEY TO MANUFACTURER-RECOMMENDED DIAGNOSIS PROCEDURES

Vehicle on Guidance

Emissions Failure Fuel System Air System EGR Catalyst

GM 1. 6L Yes Figure 1

CL Carburetor Table 1

Pulse Air Table 6

BP Table 8

TWC Table 9

GM 3.8L No CL Carburetor Table 1

Air Pump Table 6

BP Table 8

TWC/OX Table 9

Chrysler 2,2L No CL Carburetor Table 2

Air Pump Table 6

Ported Vacuum Table 8

TWC/OX No Procedures

AMC 2.5L No CL Carburetor Table 1

-- BP Table 8

TWC No Procedures

N I

w

Toyota Yes OL Carburetor Table 3

CL Air Pump Table 7

BP Table 8

TWC No Procedures

Ford l.6L Warning on Secondary Air Diversion

OL Carburetor Table 3

Air Pump Table 6

BP Table 8

TWC/OX Table 9

Toyo Kogyo No OL Carburetor Table 3

Air Pump Table 6

-- TWC/OX Table 9

Volvo/Audi/ VW/Peugeot

No CL Bosch CIS Table 4

-- -- TWC No Procedures

Saab Turbo If high HC, EGR System

CL Bosch CIS Table 4

-- On/Off Table 8

TWC No Procedures

Ford 5.0L Warning on Secondary Air Diversion

CL TBFI Table 5

(EFI) Air Pump Table 6

Sonic Table 8

TWC/OX Table 9

--

--

--

Guidance Vehicle on Emissions Failure

Nissan 2.8L No

Nissan 2,0L No

Fiat 1. 5L* --

N I -I=

*No diagnosis procedures given

TABLE 2-1

Fuel System

CL EFI Table 5

CL EFI Table 5

CL EFI

(cont'd)

Air System EGR Catalyst

Electronic TWC Table 8 Table 9

Ported Vacuum TWC Table 8 Table 9

-- TWC

The Chevette manual provides the most detailed chart for guidance on

emissions failure and we have, therefore, reproduced it in Table 2-2.

However, even this chart appears to have been formulated prior to intro

duction of three-way catalyst cars. Note that no "closed-loop" system

failures are listed as possible causes of high HC or CO, even though

such failures cause much larger increases in these pollutants, both at

idle (I/M test) and over the FTP, than some of the failures listed in

Table 2-2. This lack of specific guidance may account, in part, for

earlier CARB findings that mechanics are unable to diagnose and repair

the new three-way catalyst system.

The manufacturer recommended diagnostic methods for each of the four

subsystems -- Secondary Air, EGR, Fuel, and Catalyst -- are presented

below.

2.2 SECONDARY AIR SYSTEMS

Secondary Air Systems can be grouped by technology into systems using an

air pump and those using a pulse air valve. Air Pump systems are used

in conjunction with three-way catalysts primarily by domestic manufacturers.

Most foreign manufacturers, especially European ones, either do not use

any secondary air at all or else utilize pulse air systems. The only

domestic vehicle using a pulse air system currently is the Chevette 1.6L,

while most other domestic vehicles use air pumps. Toyota is the only

manufacturer that utilizes "closed-loop" secondary air systems where the

air pump output is modulated by the oxygen sensor. Accordingly, the

diagnostic method for Toyota vehicles are described separately.

Table 2-3 presents the diagnosis of air pump equipped and pulse air valve

equipped secondary air systems. The air pump systems consist of:

• An air pump driven by the engine

• A "diverter valve" that can divert the air to atmosphere under vacuum activation

2-5

TABLE 2-2

POSSIBLE CAUSES OF EMISSIONS TEST FAILURES

Excessive Emission

Hydrocarbons (HC)

Corban monoxide {CO)

Oxides of nitrogen {NOx)

Explanation

Execessive hydrocarbons ore caused by on air/ fuel mixture that is not burning completely.

Excessive carbon monoxide emissions ore due to o mixture that is rich.

Excessive oxides of nitrogen ore generally due ta high temperatures in the combustion chamber.

Possible Causes

• Engine not at normal operating temperature

• Disconnected, obstructed, leaking, or mis-routed vacuum hoses

• Vacuum leaks

• Maladjusted idle speed

• Maladjusted idle mixture - if plugs ore removed

• Maladjusted initial spark timing

• Spark plugs, wires or distributor cop

• Improper operation of AIR or Pulsoir system

• Lead contamination of cotolytic converter (check for absence of filler neck res trictor)

• Engine not at normal operating temperature

• Maladjusted idle mixture if plugs ore removed

• Improperly adjusted/sticking choke

• Stuck PCY valve or obstructed PCV hose

• Lead contamination of catalytic converter cperotive Thermoc

"Exce;sive emissions of bath hydrocarbons and carbon monoxide are related to on extremely rich air/fuel mixture. A rich air/fuel mixture increases CO emissions, but if the mixture 1s too rich, it will not burn completely. This unburned fuel contributes ta h,gh hydrocarbon emissions. Check for possible causes as stoled in the HC and CO section. Check co-related cous,:es first.

SOURCE: 1981 Chevrolet Chevette Shop Manual, p. 6E-6.

TABLE 2-3

DIAGNOSIS PROCEDURES FOR AIR INJECTION SYSTEMS (Except Toyota Closed-Loop AI)

Air Pume_ Pulse Air

Application: GM 3.8L, Chrysler 2.2L, GM 1. 6L Ford l.6L, Toyo Kogyo, Ford 5.0L

Functional Check 1. Physical inspection - pump, belt, excessive 1. Physical inspection: noise, hoses and vacuum lines for deteriora a) noise (hiss) hoses and/ortion, vacuum hose routing

check valve

b) heat failure - check valve

2. Check valve 2. Apply vacuum upstream of check valve and measure time rate ofa) diagnosis: inoperative pump and/or

N vacuum leakage. Replace if valveheat failure symptoms

I -..;J does not hold vacuum for 2

b) check by blowing through valve seconds.

3, Air management valve(s) - operational check

a) To exhaust manifold during cold~start

b) To catalyst after warm-up

c) Diversion to atmosphere/air cleaner during deceleration or closed-loop system failure

Notes: 1. Function may be checked during normal warm-up by removing appropriate hoses

2. Electrically operated valves checked via disconnection of solenoids

3. Vacuum control valves may be operated by applied vacuum signals.

• A "switch valve" that supplies air to the exhaust manifold under cold conditions and switches the air to the oxidation catalyst (in TWC/OC catalyst systems) or to the atmosphere (in TWC only catalyst systems)

• A "check valve" that prevents blow back of engine exhaust gases into the air supply hoses

• Electrical or thermal vacuum switches to turn on this control vacuum

The diagnostic method begins with a physical inspection of the belts and

hoses connected to the air pump. "Check valve" operation is evaluated

by blowing through the valve and confirming that air flows only in one

direction. Diverter valve and switch valve operation may be checked by

removing appropriate hoses to confirm that air is supplied to the exhaust

manifold during cold-start and to the catalyst after the engine is warmed

up. (All cars in the reference list utilizing air pumps also utilized a

TWC/OC catalyst system.) Since both check and switch valves are vacuum

activated, manufacturers recommend checking the vacuum hose connections

and the presence of vacuum at the valves under appropriate conditions,

as described in the table.

Pulse air systems were represented by single model in the reference list

--the Chevette. The only checks were visual inspection and checks for

hissing noises (indicative of check valve failure). The only diagnostic

for the check valve was through application of a vacuum. EEA studied

manufacturer recommended diagnostic procedures for other vehicles using

pulse air (e.g., the Chrysler 2.6L) and found essentially similar recom

mendations.

Toyota's 1.8L engine employs a unique secondary air system that is

modulated by the computer. The computer utilizes the oxygen sensor signal

to modulate vacuum to the diverter valve causing intermittent dumping of

air. Thus, all functional checks applicable to conventional air pump

systems must be performed and the intermittent modulation of the air

2-8

supply checked as well. Table 2-4 shows the recommended diagnostic

procedures for the Toyota. Note that the catalyst is provided with

temperature sensor that causes the computer to divert air under overtem

perature conditions.

2.3 EGR SYSTEMS

EGR systems were found on all cars in the reference except for three

cars equipped with the Bosch CIS fuel injection system. One other vehicle

the Saab Turbo -- was equipped with the Bosch CIS system and a simple

on-off EGR system.

All EGR systems share the following common performance criteria:

• EGR off when the engine is cold

• EGR off at idle

• EGR off when engine is at wide-open throttle.

All EGR systems studied are vacuum activated and, hence, the third condi

tion is automatically met as there is no vacuum at wide-open throttle.

Vacuum is cut-off to the EGR valve at cold engine temperature by a thermal

vacuum switch (TVS) or an electrical vacuum solenoid activated by the

computer. In back-pressure EGR systems, vacuum is modulated by a back

pressure sensor that increases EGR flow proportionally with engine load,

so that there is no EGR at idle. In ported-vacuum systems, the EGR vacuum

is supplied from a specially constructed port near the throttle blades

so that the port is not exposed to engine vacuum at idle. In computer

controlled EGR systems, the control vacuum is modulated electrically by

the computer, but the remainder of the EGR system is identical to ported

vacuum systems.

Diagnostics for all EGR systems follow similar guidelines, as shown in

Table 2-5. The EGR diaphragm is mechanically checked for free-movement.

The presence of vacuum at the EGR control port is measured at some non-

2-9

TABLE 2-4

DIAGNOSIS OF TOYOTA CLOSED-LOOP AIR INJECTION

Air Injection Diagnosis

1. Physical and functional checks (see Table 2-3)

Note: air bypass at cold start

2. Check for air fluctuation at bypass hose (normal operating temperatures)

3. Check catalyst over-temperature protection

a) Short pins TWC/E of service connector (near ignition coil inside engine compartment) and check for continuous air bypass (simulates over-temp)

b) Measure resistance of catalyst temperature sensor

Note: After 1-3, vacuum and mechanical components are functional

EGO Sensor Test

1. After completing air inJection diagnosis, connect voltmeter to S6rvice connector pin O and check for fluctuating voltage

X

2. If fixed voltage or fewer than 8 fluctuations in 10 seconds:

a) Check (or recheck) air injection components, hoses, wiring;

b) if a) okay, replace EGO sensor

ECM - No diagnostics provided

2-10

TABLE 2-5

DIAGNOSIS OF EGR SYSTEMS

Type/ AEE_lication

NO Failures xNoted

Driveability Complaints Noted

Diagnosis Procedures*

Back-pressure GM l.6L Yes No 1. Check hose routing

GM 3. SL

AMC 2 .SL

Toyota

Ford l .6L

No

No

No

No

No

No

No

Yes

2.

3.

Check vacuum signal hose (carburetor to EGR valve)

- obstruction

- measure vacuum supplied

Check free movement of EGR diaphragm

I\)

I ..... .....

4. Ford

- apply vacuum to control port; valve should not hold vacuum

- check for EGR passage obstruction

a) elevate backpressure by partially blocking exhaust

b) apply control vacuum and verify engine roughness at idle (high EGR rates)

5. TVS (if present) remove opening in heat bath

and check

6. AMC - check valve movement rapid deceleration

during

*Procedures generally applicable across manufacturers, although specific implementations may vary. Major differences in procedure are noted.

TABLE 2-5

(continued)

Type/ NO failures Driveability Complaints AE£lication xNoted Noted

Ported Vacuum Chrysler 2.2L No No

Nissan 2.0L No No

I\) I ...... I\)

SONIC Ford 5,0L No No

Electronic Nissan 2.8L No No Modulation

*Procedures generally applicable across manufacturers, although specific implementations may vary. Major differences in procedure are noted.

Diagnosis Procedures*

1. Physical inspection as for back-pressure system.

2. Check movement of EGR valve during rapid deceleration (Chrysler)

3. Check valve movement \vith externally applied vacuum signal (Chrysler). Check movement at high idle with cold and warm engine (Datsun).

4. Coolant temperature valve checked in cold temperature bath

5. Simplified fault tree given for determining con~onent problem (Chrysler)

1. EEC system check (see Table 5)

2, Physical and functional check as for ported vacuum system

1. ECCS check (see Table 5)

2. Physical and functional check as for ported vacuum system

idle condition, and the absence of vacuum at idle is checked. In back

pressure systems, the exhaust is partially blocked and vacuum applied to

the EGR valve from an external vacuum source so that the presence of EGR

can be inferred from engine roughness. For a ported-vacuum system, the

same test can be performed without any exhaust blockage. In computer

controlled systems, the lack of appropriate vacuum signals at the EGR

valve indicates malperformance of either the electrically controlled

vacuum solenoid or some fault with the computer; check out of computer

functions is described in the next subsection.

2.4 FUEL SYSTEMS

Unlike EGR and secondary air systems, fuel systems display considerable

diversity in both technology as well as in recommended diagnostics. Tech

nologically, fuel systems can be grouped into the following categories:

• Open-loop carburetors

• Mechanical fuel injection (Bosch CIS)

• Electronic fuel injection

The first category, open-loop carburetors, is essentially similar to

conventional carburetors on pre-three-way catalyst cars and most diagnos

tics are identical to those specified for conventional carburetors.

Table 2-6 shows the recommended diagnostics for such carburetors and the

principal additions to the diagnostic method is due to the presence of

the high altitude compensation (HAC) valve. The valve is usually checked

through the opening or closing of vacuum passages at high altitude.

Closed-loop carburetors employ an electrically operated solenoid that

modulates air fuel ratio. In most closed-loop carburetors, no electrical

signal to the carburetor results in a rich-mixture while a continuous

signal to the solenoid results in a lean mixture. The computer modulates

the electrical input to the solenoid and the duty cycle of this input is

determined by the oxygen sensor. During warmup, when the oxygen sensor

2-13

TABLE 2-6

DIAGNOSIS PROCEDURES FOR OPEN-LOOP CARBURETORS

Application: Toyota (closed-loop air injection) Ford l.6L Toyo Kogyo

Diagnosis Procedures (All): 1. Troubleshooting chart keyed to driveability/

fuel economy complaint (only).

2. Conventional carburetor diagnosis/repair

a) Physical inspection - free movement of accelerator, choke linkage, etc.

b) Off-vehicle inspection - cleanliness, check for blokage in fuel passages, check float, needle valve, fuel pump diaphragm, etc.

3. Idle speed and timing check

4. Idle mixture adjustment via lean-drop method

5. High altitude compensation (HAC) valve

Toyota: 1) Determine high/low altitude position of HAC by blowing through port on top of valve. Closed passage is low altitude position.

2) At high altitude, timing retarded from 15° to 8° BTDC when distributor HAC subdiaphragm hose is disconnected/ plugged.

Ford: 1) Connect vacuum gauge to air inlet on valve.

2) Normal conditions: vacuum present above 3500 ft.

Toyo 1) Remove air cleaner and start engine. Kogyo:

2) Blind slow port on air hone; idle rpm drop at high altitude (above 1600 ft.)

2-14

is not activated, the computer provides a fixed predetermined duty cycle

to the solenoid.

Manufacturer-recommended diagnostics for closed-loop carburetors essentially

utilize the dwell meters' ability to read the duty cycle under different

operating conditions. GM is currently the only manufacturer to provide

extensive on-board diagnostics that can be accessed without any special

tools by the mechanics. Procedures for GM cars are based on utilizing

the on-board diagnostics. Table 2-7A provides GM recommended methods

(the AMC 2.5L is built by GM) for diagnosing the fuel system and computer.

GM also provides a system performance check if the diagnostics are not

working, based on connecting the dwell meter to the carburetor solenoid

and observing its behavior. Tests include making the carburetor meter

rich by choking the air flow and checking dwell meter response (for fixed

low dwell condition) or by leaning out the mixture (for fixed high dwell

condition). The system that is performed at high speed idle (@3000 rpm)

to insure fully warmed-up operation.

Chrysler utilizes the same type of control system and a very similar,

although slightly more innovative test method. With the dwell meter

attached to the solenoid, Chrysler recommends disconnection of the oxygen

sensor harness. The human body is then used as a surrogate oxygen sensor

-- with a finger inserted into the harness, the positive terminal of the

battery is touched with the other hand, indicating a rich mixture. If

the system is operating correctly, the computer drives the engine lean,

causing the dwell meter to read high and engine rpm to drop. When the

harness is ground, the computer drives the engine rich with exactly

opposite effects. Chrysler's recommended diagnostic procedure is outlined

in Table 2-7B.

The Bosch (CIS) Fuel Injection System is conceptually similar to a closed

loop carburetor in the operating principles of the closed-loop system.

Just as the solenoid modulates the base air-fuel ratio in the feedback

2-15

TABLE 2-7A

DIAGNOSIS PROCEDURES FOR CLOSED LOOP CARBURETOR (GM C-4 System Only)

Application: GM 1. 6L GM 3.SL AMC 2. SL

Inspection Procedure: 1. Activate on-board diagnostics (displayed on check engine light) (a) First trouble code (code 12) indicates diagnostics functional (b) Read trouble code and refer to code-specific fault trees

c~11 pages) for detailed diagnosis procedures.

2. If no trouble code, operate engine (up to 15 n1in.) to activate check engine light and store trouble code. Then repeat Step 1.

3. If diagnostics not functional or no trouble code, use System Performance Check.

I\) t _. 0-. Diagnosis Procedure: Equipment - Dwell meter, tachometer, digital voltmeter

System Performance Check

1. Performance Diagnosis (a) RPM drop when M/C solenoid disconnected (@3000 rpm)

TABLE 2-7A (continued)

I\)

I ..... --.J

2. Component Diagnosis

(a) Choke engine at idle. Dwell increases - Check for air or vacuum leak, EGR operation, vacuum hose routing

No dwell change - Faulty EGO sensor, ECM, or wiring harness.

(b) Check TPS movement and for low coolant Check coolant temp sensor resistance If no dwell change with coolant sensor shorted, then faulty EGO sensor or wiring, coolant sensor wiring, or ECM/ECM wiring

(c) Lean engine via vacuum leak. Dwell changes - carburetor calibration

No dwell change - faulty EGO sensor or ECM

3. Repair, repeat from Step 1.

TABLE 2-7B

DIAGNOSIS PROCEDURES FOR CHRYSLER CLOSED-LOOP CARBURETOR

Application: Chrysler 2.2L

Diagnosis Procedure: 1. Equipment - dwell meter, timing light, digital voltmeter

2. Verify that Electronic Spark Advance Computer (ESC) is functional

a) If vehicle won't start, diagnose ignition system, then continue

b) Check spark

3. M/C Solenoid test - replace if fails a) and b)

a) Disconnect (open) @2000 rpm: rpm rise

b) Reconnect, ground ECU pin ( # 15) : rpm drop

4. ECM test - replace if fails c) and d)

a) Connect voltmeter to M/C solenoid

b) Disconnect EGO sensor harness

c) Ground sensor harness: voltage >9V

mm should rise d) Insert finger into EGO harness; with other

hand touch positive terminal of battery: voltage

carburetor, a "frequency valve" modulates the fuel metering pressure

which determines the quantity of fuel injected. Table 2-8 outlines the

recommended methods for these vehicles with the Bosch CIS system. Note

that Saab, Audi, and VW utilize a specialized tester that cycles the

computer with the engine off. However, Volvo provides a diagnostic method

that utilizes a dwell meter monitoring the frequency valve's input signal.

Conceptually, the diagnostic method is identical to the system performance

check utilized by GM for the feedback carburetor (Table 2-7A) except

that in this system, high dwell is used to drive the mixture rich and

low dwell to drive the mixture lean --i.e., the opposite of the duty

cycle used in carburetors. Volvo is unique in that it recommends

monitoring CO ahead of the catalyst -- a special sample line is provided

on Volvos -- to determine if the air-fuel mixture is actually rich or

lean.

Closed-loop electronic fuel injection systems offer the most specialized

diagnostic procedures of all fuel systems surveyed. The Ford 5.0L engine

equipped with Central Fuel Injection (CFI) requires a special test unit

called the "Rotunda Tester" which plugs into the existing wiring harness

on the car. The tester automatically activates various computer circuits

in sequential order and monitors engine response to check the different

emission control components. The Nissan 2.8L engines also utilizes a

special tester, the "ECCS Analyzer," to perform a system check similar

to the one performed by the Ford "Rotunda Tester." However, both the

2.8L and Nissan 2.0L provide an inspection lamp on the engine control

unit (computer) that flashes whenever the closed-loop system is operating.

Diagnostic procedures for the Nissan 2.0L engine utilize this inspection

lamp and are detailed in Table 2-9. Note the conceptual similarity with

Chrysler test for feedback carburetors. Instead of reading the dwell

meter response, the inspection lamp provides the visual clue to checking

closed-loop operation. As with the Chrysler test, Nissan recommends the

oxygen sensor be disconnected and the harness grounded to drive the system

rich. In the case of the Nissan, correct operation of the computer would

2-19

TABLE 2-8

DIAGNOSIS PROCEDURES FOR CLOSED-LOOP FUEL INJECTION (Bosch K-Jetronic CIS)

Application: Volvo, VW, Saab Turbo, Peugeot, Audi

Recommended Equipment: Volvo - CO analyzer, high impedance dwell meter Saab - Bosch KDJE-7453 dwell meter, CO analyzer Audi - Siemens 451 or VAG 1367 testers (only)

Diagnosis Procedure: Volvo Saab Turbo/Audi/VW

1. Cold-start with EGO disconnected 1. Connect test instrument to test socket Connect dwell meter to test socket on relay panel and power supply (Saab);

connect instrument to EGO test terminala) Check open-loop baseline and insert manually switched test relayof frequency valve (dwell spec.) to fuel pump relay socket (Audi) (instruments simulate engine operation)

2. Warm-up, check/adjust idle speed I\.) I a) Attach CO analyzer ahead of 2. Engine off

0 I\.) catalyst at test fitting a) Frequency valve audible; else check

b) Abnormal CO - adjust FI idle valve and wiring. If okay, replace mixture ECM

b) Check open-loop duty cycle. If ~60%,3. Reconnect EGO Sensor okay. Else, faulty EGO sensor or a) Normal: CO 75%, else faulty ECM/ECM harness

d) Disconnect ground - if duty cycle drops4. Dwell nonual/CO >1%, check EGO below 50% and returns to 60%, okay.

sensor mounting, exhaust leaks. Else faulty ECM/ECM harnessCheck mechanical FI

3. Engine running5. No dwell change Faulty EGO sensor or ECM a) Check full throttle enrichment

(turbo only) 6. Low dwell/ CO >1% b) Warm-up until duty cycle varies.Faulty Frequency Valve If extreme high or low duty cycle,

check EGO sensor, ECM and/or ECM7. lligh dwell/CO >1% harness.

f.'r"l11l t-u hrn c-r'\.....,,.,....,.,_,,.

TABLE 2-9

DIAGNOSIS PROCEDURES FOR CLOSED-LOOP EFI SYSTEMS

Application:

Recommended Equipment:

Diagnosis Procedure:

N I

N....

Ford S.OL

Rotunda EEC tester Wiring harness adapter Fuel Pressure Gauge Digital voltmeter

1. Attach tester to ECM via wiring harness adapter and start engine

2. Tester activates EEC components and monitors engine response

(a) Sequential test of system by Quick Test flowchart; requires some control of engine operating conditions

(b) Service codes indicated on tester panel; produces reference to detailed diagnosis procedure (154 pp.)

3. Components checked:

• Battery voltage; sensor reference voltage

• Cranking signal (EFI) • TPS • Coolant temperature sensor • Air change, temperature sensor • MAP sensor

• Barometric pressure sensor • EGR valve • AC TI1rottle Kicker • Air management system • Crankshaft position sensor • Ignition module • EGO sensor

Nissan 2.8L Nissan 2.0L

ECCS Analyzer J-28835 Exhaust gas analyzer, tachometer, timing light

1. Attach tester to ECM via 1. Physical inspection and/or wiring harness adapter and conventional diagnosis of: start engine battery, ignition system,

engine oil and coolant 2. Tester performs checks level, fuses, EFI wiring

similar to Ford Rotunda harness, vacuum hoses, etc.

3. Components checked: 2. Check/adjust idle speed and timing on fully warm engine

• Ignition (vacuum spark advance dis• EGR connected and plugged)• Fuel Pump • Idle speed control 3. Warm-up EGO sensor (run• Battery engine at 2000 rpm for• Air Flow Meter ~2 minutes). Check for• Air temperature sensor flashing of inspection lamp• Cylinder lead temperature on control unit (under-dash)sensor • Knock sensor (a) If 3 or more flashes • Crankshaft position in 10 seconds, then

sensor closed-loop system is • Road speed sensor okay. • Injector operation

(b) lf lamp does not flash(individually) check continuity in control unit/EGO sensor4. Closed-loop Control harness; replace or

(a) Inspection lamp located repair as necessary. on ECM flashes with closed-loop system.

(b) If not flashing, replace EGO sensor

(C) If still not flashing,replace ECM

TABLE 2-9 (cont'd)

Application: Nissan 2.0L

Recommended Equipment: ECCS Analyzer J-28835

Diagnosis Procedure: 4. If continuity exists but lamp does not flash, check EFI control unit:

(a) Warm-up EGO sensor at 2000 rpm

(b) Disconnect EGO sensor harness and monitor inspection lamp response:

1. lamp glows when harness is grounded 2. lamp off \vhen harness is open

(c) Replace control unit if response not normal and repeat Step 3, or else continue with Step 5,

S. With engine off, connect pins 24 and 30 of throttle valve switch harness connector

N to simulate full-throttle connection. N I

Disconnect EGO sensor harness. Start N

and warm-up engine. Insert exhaust gas analyzer into tailpipe.

(a) If CO 6%, continue with Step 6.

6, a) If engine runs smoothly, replace EGO sensor. Reconnect throttle switch and EGO harness and check inspection lamp (Step 3).

b) If engine runs roughly, check for vacuum leaks and correct as necessary, then check inspection lamp (Step 3).

c) If engine runs rough and no vacuum leaks found, adjust baseline calibration as in Step S(a), then repeat procedure from Step 5.

result in the inspection lamp turning on. Additional steps for diagnosis

include a check of throttle position sensor which can influence the

operation of the closed-loop system as indicated in Table 2-9.

2.5 CATALYST SYSTEM

Unlike the voluminous diagnostics provided for the other systems, little

information is provided by any manufacturer on the diagnosis of catalysts.

Table 2-10 provides the listing of manufacturer's recommendations for

diagnosis of catalyst malperformance -- less than half the vehicles on

the reference list had any recommendations regarding the diagnosis of

catalysts. Recommended procedures tended to be very simplistic and

primarily involved physical examination for damage or substrate meltdown

that results in blockage of the exhaust. Nissan utilized a CO check

after all other emission control systems were found to be operating

properly --i.e., a "last resort" diagnostic.

Since lead poisoning of catalysts results in their failure and none of

above tests are useful in determining if the catalyst is poisoned by

lead, EEA searched for additional data on diagnosis of catalyst poisoning.

Manufacturers were of little help -- however, the EPA recently performed

a detailed study of misfueling of cars and utilized three tests:

• Inspecting the filler neck for tampering

• Using a chemical test for identifying lead in the exhaust pipe

• Testing for lead in gasoline.

The chemical test used for identifying the lead in the exhaust pipe was

the commercially available "Plumbtesmo" test where filter paper soaked

in a special solution changes color in the presence of lead. The lead

content of the gasoline in the vehicle's tank was checked by withdrawing

a sample and checking for lead by the atomic absorption method in the

laboratory.

2-23

TABLE 2-10

DIAGNOSIS OF CATALYST SYSTEM

Application Diagnosis Procedure

GM 1.61 • Noted as possible cause of HC and/or CO failures

• Check for absence of filler neck restrictor

GM 3 .8L • Physical inspection of converter canister, exhaust pipes, muffler

Toyo Kogyo • Physical inspection of canister, test for exhaust leakage

Audi • If rattle or driveability problem (low power output, idle speed drop, or stalling]

- remove

- hold up to light and look through to check for melted substrate

- tap canister to check for substrate movement

Ford 5.01 • Check for exhaust system restriction

Nissan 2.81 • Physical inspection

Nissan 2.01 • Warm-up catalyst 4 minutes at 2000 rpm (1) return to idle and measure exhaust

co (after catalyst) (2) normal is 0.3%, check EFI system and repeat (

(4) if still >0.3%, replace catalyst

2-24

The results of the test are displayed in Figure 2-1. Each test failed

approximately 175 cars, but the failures were not identical. As can be

seen from the figure, only 74 of the vehicles failed all three tests,

whereas 279 cars failed at least one test, and 149 cars failed at least

two tests. If we assume that only cars failing all three tests were

misfueled and their catalysts were poisoned, then any of the three tests

results in over a 50 percent error rate. On the other hand, if we assume

that vehicles are misfueled if they fail any one of the tests, the maximum

detection rate is 66 percent (for the "Plumbtesmo" test). Conversations

with EPA field staff revealed that "Plumbtesmo" sample was sensitive to

ambient conditions such as humidity and temperature and would be a diffi

cult test to implement for day-to-day use by mechanics. Testing for

lead in gasoline is clearly beyond the scope of any mechanic, leaving

only the inspection for a tampered filler neck restricter as a viable

test for field use. However, based on EPA's test results, it is difficult

to make any conclusive comment on its usefulness as a diagnostic tool

for catalysts.

2-25

fIGURE 2-1

POSITIVE

PLUMBTESMO >0.05 g/ga/

/184 CARS TOTAL) { 163 CARS

49 CARS

49 CARS

N I f\) O'I

TAMPERED FILLER RESTRICTDR / 155 CARS TOTAL)

VEHICLES REQUIRING UNLEADED FUH [ 2637 TOTAL)

COMPARISON Of MULTIPLE INDICATORS :0

()-r, f'A'T'A T V'2'T' llnTc'ni.ry~I('

3. SURVEY OF FIELD MECHANICS

3.1 INTRODUCTION

A survey of field mechanics was initiated by EEA in order to understand

the procedures currently used by them to repair emission control malfunc

tions in three-way catalyst cars. The survey also elicited their concerns

regarding data availability, usefulness and shortcomings of manufacturers

recommendations and difficulties in implementing available procedures.

The purpose of the survey was to obtain some insight into mechanics'

diagnostic methods so that generalized diagnostic procedures could be

designed to address mechanics' abilities and concerns. The resource

limitations of the project made it impossible to conduct a formal, statis

tically valid survey. Rather, this survey was primarily for informational

purposes to aid in the design of diagnostic procedures and the data

presented here should be construed as indicative of trends.

For the survey, certified Class A .mechanics were interviewed about their

knowledge of the diagnosis and repair of emission control systems. The

interviews were conducted by J.D. Power and Associates using a question

naire and guidelines developed by EEA. Sixty-three mechanics were inter

viewed in three cities in California -- Los Angeles, San Diego and San

Francisco -- with over half the interviews conducted in Los Angeles, so

that geographical differences among mechanics would be apparent. Inter

views were restricted to certified Class A mechanics as these credentials

are required for mechanics to repair vehicles failing the emission

inspection. In order to capture the diversity of mechanics' abilities,

the survey sample included mechanics from dealerships, repair chains

(such as Sears, K-Mart) and independent repair facilities. All mechanics

interviewed had Motor Vehicle Inspection Program (MVIP) or Motor Vehicle

Pollution Control (MVPC) experience. Mechanics were individually

3-1

interviewed using an open ended questionnaire by representatives from

J.D. Power. These interviewers were not trained mechanics, but had

general familiarity with emission control systems and were briefed in

detail about the performance of these systems by EEA staff. Given the

limitations in knowledge and the time constraints facing the interviewers,

it was not possible to probe several ambiguous statements by mechanics.

Hence, some of the results appear contradictory, but reflect the survey

data as collected.

The questionnaire employed by the interviewers provided a logical sequence

of queries on the mechanics' background, work experience, general approach

to diagnostics, specific information on the four emission control systems

of interest (Secondary air, EGR, fuel and catalyst systems) and some

general questions to decipher areas where mechanics feel they could use

information. The responses of the mechanics were tabulated and reported

in detail by J.D. Power in Appendix A of this report. This section

summarizes the important results of the survey.

3.2 MECHANICS' EXPERIENCE

Of the sample of 63 mechanics interviewed, 23 worked at dealerships, 25

worked in independent garages and 15 worked at repair chains. The sample

was chosen to cover a wide variety of experience levels ranging from

five years to over 35 years. The average for the sample was 16.5 years,

with about half the sample having an experience range of 5 to 14 years.

Additionally, mechanics were asked about how long they were certified by

the BAR. Table 3-1 shows the distribution of mechanics in the sample by

number of years of BAR certification. Since BAR certification for a

MVPC Class A license has been in existence since 1973, the data in Table

3-1 showing 41 percent of mechanics being certified longer than 10 years

appears erroneous; however, mechanics may have confused the MVPC license

with the more general BAR mechanics license which has been in existence

for a much longer time.

3-2

TABLE 3-1

EXPERIENCE OF MECHANICS SURVEYED (Number of years with BAR certification)

Percent

Less than 5 years 22 5-9 years 37

10-14 years 20 15-19 years 10 20-24 years 4

more than 24 years 7

3-3

Training and education received by mechanics varies considerably and

depends primarily on the type of service facility. New car dealership

provide extensive training with classes every few months sponsored by

the manufacturer, usually at a school and through local seminars. The

training, however, is usually limited to the brand(s) of cars sold at

the dealership in which the mechanic is employed. Independent garage

mechanics report that their training was at vocational schools, although

many of them have had previous experience at dealerships where they

received the training mentioned above. On-the-job training depends on

the nature of incentive provided by the owner to the mechanic to attend

each training sessions.

In general, owners who have invested in service centers with specialized

equipment for repair of emission control devices do send their mechanics

for training in the diagnostics of emission control systems. Mechanics

at chain stores appear to be least trained. Although they have access

to the same training seminars as the independents, mechanics at chains

are given no time or incentive to attend such seminars. Typically, chain

shops did not repair cars with complex emission control systems and hence

mechanics saw little point to their learning about such systems.

A second major point made by mechanics was that their best education was

from the "hands-on" work that they do rather than from seminars.

Typically, mechanics experiment with new systems and learn through

experience; since the new three-way catalyst systems are only two to

three years old, they are still being repaired (under warranty) at dealer

ships and hence, independents and chain shop mechanics have not had the

exposure that dealership mechanics have to these systems. Most mechanics,

but not all, surveyed had some experience in the repair of electronic or

"feedback type" emission control systems. The experience and knowledge

of dealership mechanics about these systems is readily apparent in their

responses to the survey.

3-4

3-3 APPROACH TO DIAGNOSTICS

Mechanics were queried on their general approach to diagnostics prior to

more detailed questioning on specific emission control systems. Questions

were asked on:

• Customer contact

• Preliminary check of the vehicle

• Areas of specialization

• Availability of manuals and tools

• Familiarity with the inspection/maintenance test

• Extent of emission control repair performed.

Dealership and chain mechanics rarely, if ever, deal with the customer.

Monetary limits and vehicle driveability problems are discussed by a

service writer who tells the mechanic what the customer wants or does

not want. Independent garage mechanics, on the other hand, often deal

with the customer directly and obtain their inputs on driveability

problems and the nature of repair work to be performed.

If a vehicle that has failed the I/M test comes in for repair, all

mechanics perform a preliminary retest to check the values using an HC/CO

analyzer. Los Angeles based mechanics are provided with an inspection

sheet that records the emissions readings of the vehicle as well as the

emission standards the vehicle must meet before it can be certified.

The initial retest used by mechanics is used as an indicator of specific

problem areas. Mechanics will, in general, work only on vehicles in

which they have some experience. As a result, chain stores often do not

work on complex emission controls such as fuel injection systems or feed

back carburetors. Since Federal law requires a 5-year, 50,000 mile

warranty on emission control systems, many independent garages and chain

shops will recommend that owners of vehicles with the more recent complex

emission controls take their vehicles to dealerships for warranty service.

Mechanics also appear to avoid specific vehicles which have given them

great difficulty in the past.

3-5

Specialization seems to be widespread among most mechanics. As noted

previously, chain shops do little more than tune-ups on vehicles with

the conventional emission control systems. Independent garages often

have individual mechanics specialize in certain types of systems such as

fuel injection or certain makes of cars with relatively more complex

emission control systems. Dealership mechanics very obviously must

specialize in the vehicle types sold by the dealership, although they

receive exposure to other vehicles that are traded in for resale by the

dealer. However, many of the dealership mechanics did not know about

system peculiarities in late model vehicles other than the ones sold by

the dealership primarily because their exposure to other vehicles is

limited to the older vehicles traded in by consumers.

The survey reported that mechanics appear generally satisfied with the

availability of manuals. This comment must be read in the context of

mechanics usually having some areas of specialization in the newer, more

complex emission control systems. (Service manuals are required to be

present in all certified repair shops according to California regulations.)

A few mechanics stated that they would like to see more specific informa

tion especially about electronics and some step-by-step information on

emission control repair. This is consistent with EEA's finding that

current service manuals rarely provide diagnostic guidance to mechanics

on emission failures. If the manuals are not sufficient or do not provide

the needed information, mechanics will generally call the service depart

ment of a dealership or a manufacturer representative for additional

information. Mechanics also appear to have some trouble understanding

the certification requirements for the I/M test administered in the Los

Angeles area (San Francisco and San Diego do not require a retest by the

state facility) and, hence, sometimes call the ARB for information on

standards for specific types of cars.

Mechanics emphasize that the information in service manuals or trouble

shooting charts was secondary to the primary source of information --

3-6

experience. Most mechanics found that following the charts was laborious

and time consuming and experience generally provides the fastest way to

find a problem. Mechanics said that they used the manuals and charts on

new or unfamiliar vehicles but few mechanics admit to using a trial and

error method for diagnostics. All mechanics uniformly found the stickers

or decals under the hood to be very useful -- especially those providing

vacuum hose diagrams. Some asked that more information be provided on

the sticker like spark plug gap, CO levels and carburetor settings.

Mechanics at chain shops and independents stated meeting the cost limita

tions, rather than correct and complete repair of the vehicles, are the

primary objectives of their work. These mechanics state that they fix

only the minimum necessary for a vehicle to pass the emission test. The

state imposed repair cost ceiling of $50 appears to be the prime reasons

for this and with labor costs of $30-$40/hr., there is little leeway for

the mechanic to spend time ensuring the vehicle is up to manufacturer

specification. Dealership mechanics, on the other hand, appear to be

more willing to restore the car to specifications, possibly because much

of their work on emission control is done under warranty. None of the

mechanics interviewed stated that a lack of tools hampered their diagnos

tics, although mechanics at shops equipped with a dynamometer were

enthusiastic as they felt more competent in diagnosing cars with NOX

failures.

3.4 SYSTEM SPECIFIC DETAILS

Mechanics were questioned on their diagnostic approaches to the secondary

air, EGR fuel and catalyst systems. The interviewers were provided with

the "right" answers to questions relating to understanding of the prin

ciples of system operation and the appropriate diagnostic for each system.

In most instances, mechanics provided these answers or a "don't know"

but in some, ambiguous answers were provided. EEA concludes that mechanics

were reluctant to disclose their lack of knowledge of such systems where

such ambiguous answers were provided.

3-7

It is difficult to further summarize the mechanics' responses to questions

on specific systems beyond what is provided in Appendix A of this report.

The reader is referred to this section for details on how mechanics fix

each specific portion of the system. It became readily apparent that

most mechanics are conversant with the diagnosis and repair of EGR systems

and secondary air systems equipped with an air pump. Pulse air systems

(available on some Japanese vehicles and the Chevette) are poorly under

stood, although this may reflect the fact that many mechanics may never

have worked on cars equipped with such systems. Similar lack of knowledge

is displayed by mechanics on "closed-loop" or feedback systems, although

it is possible that the terminology may be confusing to the mechanics.

Mechanics also appear unfamiliar with differences between mechanical and

electronic fuel injection systems. Overall, mechanics tended to have

knowledge of either mechanical or electronic fuel injection systems, but

not both, reflecting the specialization in the field. Similar lack of

knowledge was reported on the newly developed internal diagnostic systems

(available on all 1981+ GM cars and some Ford vehicles). Some mechanics

responded that feedback carburetors, electronic controls, and internal

diagnostics were hard to repair, and many others provided responses that

were ambiguous at best, leading EEA to believe that it is likely that

those mechanics knew little about such systems. A surprising number of

mechanics (75%) claimed that they inspect the catalyst, while several

even claimed that they measure CO/HC readings with and without the

catalyst (by physically removing the catalyst) to examine if the catalyst

is actually functioning or not.

3.5 ADDITIONAL COMMENTS

Mechanics were allowed to make a number of additional comments, which we

have grouped into four topic areas.

I/M Test - Many mechanics appear not to know about the exact procedure

used on the I/M test, with nearly one-sixth of the sampled mechanics

3-8

giving wrong answers to questions about the test. Many mechanics in the

Los Angeles area questioned the correctness of the emission readings

(primarily because only the L.A. area requires a retest) and reported

very negative interaction with test center personnel. Many mechanics

feel that Hamilton test personnel were unqualified for their job and

performed the test unfairly. to obtain a retest fee.

Emission Standards and Control Technology - Mechanics in San Diego and

San Francisco mentioned the need for information on exactly what standards

were applicable to each vehicle in question. (Mechanics are provided

this information in the Los Angeles area.) Some mechanics requested a

tag on the vehicle identifying all the emission control equipment that

was supposed to be on that vehicle so that outright removal of this

equipment could be checked. Others even requested the specifications

for the equipment listed.

GARB Information - Some mechanics requested a local GARB office of hotline

to obtain necessary information on standards or check on manuals. Others

requested the help of the ARB "for general questions" on the test proce

dure or cost limitations.

Diagnostic Procedure - Most mechanics remain suspicious of standardized

diagnostic procedures because they feel cars are too different. Only

one mechanic in the sample saw this as a useful idea. In spite of their

troubles with feedback control systems, most mechanics did not feel that

there was a need for additional diagnostic information. Paradoxically,

many mechanics requested that the GARB provide a diagnostic on each

vehicle for them. Others felt that, given the $50 cost ceiling, there

was little they could do beyond what they were already doing.

3-9

4. DF..SIGN OF GENERALIZED DIAGNOSTIC METHODS

4.1 OVERVIEW

In this section, the methodology used to develop generalized diagnostic

procedures is detailed and the generalized procedures are presented as a

series of tables which outline the steps required to diagnose an emission

control system malperformance. It must be emphasized, however, that

these tables are not intended to be supplied to mechanics as presented

in this report, but should be used as the basic material --together with

illustrations or pictorial descriptions -- from which a handbook for

mechanics can be developed. A second major point that must be emphasized

is that these procedures are not intended to replace existing manufac

turer specified procedures, but are intended to supplement them. Thus,

questions regarding warranty of emission control systems that impose

legal requirements on manufacturers cannot be resolved through the use

of the generalized test procedures. The procedures presented in this

report, however, provide simple reliable methods that can be used on a

wide variety of "closed-loop" three-way catalyst equipped makes and

models of vehicles.

Given the wide diversity in emission control systems technology, it was

recognized that no generalized procedure could be expected to diagnose

every component of the emission control system for every make and model

available. Secondly, the development of these procedures was predicated

on the assumption that the mechanic was competent on earlier (oxidation

catalyst) technology and was therefore, starting from a knowledge base

where it was not necessary to explain the basic operating principles of

engine components such as carburetors or fuel-injection systems. EEA

recognizes that many mechanics do not, for example, understand the

operating principles of fuel-injection systems; the objective of the

4-1

procedures developed here is not to educate such mechanics on fuel-injec

tion systems, but to expand the knowledge of those who already understand

the basic principles of such systems into the area of "closed-loop" fuel

injection systems. Thirdly, given the resource constraints of the contract,

it was decided that the effort would be directed to provide diagnostics

in areas in which mechanics appear to need the most help. Accordingly,

EEA reviewed the results of the mechanics survey and the results of other

studies on vehicle malperformances to resolve the requirements of the

diagnostic procedure, as described below.

4.2 DIAGNOSTIC PROCEDURES - REQUIREMENTS

The first step in defining the requirements of the diagnostic procedures

was to identify these emission control system malperformances that cause

significant increases in emissions. It was reasoned that if a generalized

procedure should capture most, if not all, the malperformances causing

significant increase in emissions -- defined in this study as causing a

vehicle to fail the FTP or I/M emission standards by a margin of 15 per

cent or greater -- such a procedure would be of greatest benefit to the

CARB. Accordingly, the results of a recent study performed by Systems

Controls Inc., (SCI) under contract to the CARB was reviewed.

In the SCI study, vehicle emissions were measured on the FTP and the I/M

idle test on ten vehicles equipped with three-way catalyst "closed-loop"

systems. Each vehicle's emissions were measured with all systems normally

operating and also with a number of intentional malperformances on the

"closed-loop" system with emissions for each malperformance measured

individually. Table 4-1 shows the effects of each disablement type on

the five vehicles in the sample equipped with feedback carburetors, while

Table 4-2 shows similar data on the five vehicles equipped with electronic

fuel-injection systems. For each displacement, the table shows whether

the vehicle failed the FTP and I/M test (by a 15 percent margin) with a

yes or no. Note that many malperformances made the vehicles (especially

fuel-injected vehicles) undriveable.

4-2

-- -- --

TABLE 4-1

EMISSIONS FAILURES DUE TO INTENTIONAL MALPERFORMANCE (FTP and I/M Test) Carburetted Cars

Model Year 1981 1981 1981 1981 1981

Make/Model Olds Cutlass Ford Granada Ford LTD Plymouth Reliant Chevrolet Citation

Engine 3,8L-V6 2.3L-4 5.8L-V8 2. 2L-4 2. SL-4

Fuel System FBC FBC WC FBC FBC

Disconnections FTP I/M FTP I/M FTP I/M FTP I/M FTP I/M

Oxygen Sensor Yes 11 No No No No No No No Yes 11 No

Coolant Sensor Yes Yes Yes 11 No Yes Yes Yes No Yes Yes

Throttle Position No No Yes Yes No No NA Yes 11 Yes.i::: I Sensor w

Manifold Pressure No No No(?) Yes No No NA Yes Yes Sensor

Electronic Control NT Yes Yes ND Yes(?) No NT Unit

Idle Speed Control No No NA NT No No No No

Electronic Spark Yes Yes NT ND ND Yes Yes Control

Carburetor Solenoid Yes Yes No(?) No No No Yes No Yes Yes

Ground NT Yes Yes Yes Yes ND No No . 1/ - NO failure only NT - Nol Tested NA - Not Applicable ND - Not Driveable/Would Not Start

-- --

TABLE 4-2

EMISSIONS FAILURES DUE TO INTENTIONAL MALPERFORMANCE (FTP and I/M Test) Fuel-Injected Cars

Model Year 1981 1982 1982 1982 1982

Make/Model Lincoln Mark VI Toyota Supra Cadillac deVille BMW 528E Datsun 28OZ

Engine 5.0L-V8 2. 8L-6 4 .1L-V8 2. 7L-6 2. 8 L-6

Fuel System TBI EFI TBI EFI EFI

Disconnections FTP I/M FTP 11!__!_ FTP I /~1 FTP I/M FTP I/M

Oxygen Sensor No No No No No No Yes 11 Yes Yes 11 Yes

Coolant Temperature ND* ND Yes 11 No Yes Yes ND Sensor

-I=

-I= I Throttle Position ND No No No No No No No No

Sensor

Manifold Pressure Yes Yes ND Yes Yes ND ND or Airflow Sensor

Air Temperature Yes Yes No No Yes Yes No No No No Sensor

Ground ND ND Yes Yes NT ND

Idle Speed Control NT NA Yes Yes No No Yes No

*Driveable when shorted.

1/ - NO failure only NT - Not Tested NA - Not Applicable ND - Not Driveable/Would Not Start

As can be seen from Table 4-1, the carburetted systems are sensitive to

malperformances of several components, notably the coolant temperature

sensor, the carburetor solenoid, the computer and the ground connection

for the computer. In some cases, the oxygen sensor appears to cause

increases primarily in NO emissions, while the throttle position sensor X

occasionally cause increases in emissions. The Chrysler vehicles do not

bypass secondary air under any malperformance mode and, hence, no defects

can be distinguished in the I/M test. Table 4-2 shows that fuel-injected

systems (with the exception of the Cadillac Seville) become undriveable

when an intentional and malperformance is introduced or else no increase

in emissions is observed. The oxygen sensor causes some emission failures,

as does the coolant temperature sensor. Failure of the computer always

results in fuel-injected cars becoming unstartable. Note that the new

Cadillac fuel-injection system continued to run under all other malperfor

mance models, although with high emissions. This can be attributed to

"fail-safe" design where the computer recognizes malperformances and

operates under a failure mode. The Cadillac also provides visual warnings

on failure with internal diagnostics (available on all GM cars) that can

be accessed by the mechanics.

Based on these tables, EEA concluded that the fuel system diagnostic

needed to consider:

• The oxygen sensor

• The coolant temperature sensor

• The computer

• The computer ground

• The throttle position sensor

• The manifold pressure sensor or airflow sensor (for fuelinjected vehicles only).

Based on the mechanics survey, EEA concluded that most mechanics understood

EGR systems and secondary air systems on older cars but could use some

information on more recent changes to these systems, e.g., backpressure

4-5

EGR and the inclusion of the switch valve in the secondary air system

for "closed-loop" three-way catalysts. Mechanics were less knowledgeable

in the operation of the closed-loop system and many were clearly unquali

fied in electronic fuel injection systems and internal diagnostics.

Accordingly, EEA devoted a greater effort in providing generalized diag

nostic procedures for such systems than for EGR, secondary air and open

loop fuel systems. Finally, our literature review and the mechanics

survey revealed no promising methods currently available for diagnosing

malperforming catalysts; EEA, therefore, has attempted to develop tests

for catalysts based on the expertise of their lead engineer and their

consultant, Mr. Gary Casey.

4.3 GENERALIZED TEST PROCEDURES

Based on our review of manufacturer recommended test procedures, it was

obvious that there were several similarities between the different manufac

turers' recommendations. In fact, the procedures for diagnostics on

secondary air systems (except for Toyota) and EGR systems who found to

be nearly identical between manufacturers. In fuel systems, there were

several tests that were common to the common technology groups using

feedback carburetors and mechanical fuel-injection systems, although

there was less commonality in the recommended diagnostic procedures by

the different manufacturers. As stated above, no substantive procedures

were available for the diagnosis of catalyst malfunction.

4.3.1 Basic Flowchart

In our development of the procedures, it was apparent that a preliminary

description of system operating would be required since the survey results

showed that many mechanics do not understand the operating principles of

"closed-loop" systems. A key aspect of these systems is that the computer

often controls the secondary air, EGR and fuel systems and a malperformance

in the fuel system (especially the closed-loop portion) often causes the

computer to shut down EGR and divert secondary air to atmosphere.

4-6

Table 4-3 outlines EEA's flowchart for the generalized diagnostic proce

dures. Note that the system description is listed first. Conversations

with manufacturers reveal that a pictorial description of the operation

of closed-loop systems is recommended. Although such a description is

not included in this report, many manufacturers have provided this as

written materials for seminars -- for example, both GM and Bosch provide

a pictorial representation of the operating principles of "closed-loop"

systems. Such standardized representations are useful in aiding the

mechanics understanding of the system. Note that the sequence of diag

nostics is specified, since malfunctions of mechanical components in the

secondary air system or EGR can cause the fuel system to behave erroneously.

4.3.2 System Specific Diagnostics

The procedures developed by EEA are widely applicable and require no

special tools other than the ones required by BAR for licensed Class A

mechanics. The procedures are presented in Tables 4-4 through 4-12 and

recommend checks that must be performed in the sequential order of their

appearance. The generalized procedures assume that the mechanic is

familiar with the conventional (oxidation catalyst) emission control

technology and has an understanding of the operating principles of the

overall system. In all cases, tests are performed on warmed-up cars.

Diagnostic procedures for the secondary air system are shown in Table 4-

4. The procedures are derived from manufacturers recommendations and

are relatively simple. Essentially, the procedure consists of ensuring

that the air from the air pump goes downstream to the catalyst when the

car is warmed-up for dual-bed catalyst systems and to the atmosphere for

single-bed catalyst systems. A simple schematic of a typical secondary

air system for a dual-bed catalyst vehicle is shown in Figure 4-1. The

diagram indicates the major components of such systems and the mode of

operation under cold and warmed-up engine conditions.

4-7

TABLE 4-3

BASIC REQUIREMENTS FOR DIAGNOSTIC METHOD

System Description/Mechanic Orientation

Components

Connections

- Method of operation

Sequence of Diagnostics

(1) Secondary Air System

(2) EGR

(3) Fuel System

(a) Performance Test

(b) More Specialized Tests

(4) Catalyst

System Performance Test For Each System

- Methodology

Test Description

- Tools needed

Test Response And Action For Each Test

- List of possible responses to each system performance test

Reasons for the response

Recommendation for repair or alternative action

4-8

TABLE 4-4

SECONDARY AIR SYSTEMS WITH AIR PUMP

Ensure air pump is connected and belts are tight. Check for any cracked

or disconnected hoses in the air system. Replace as necessary.

Performance Test

(1) Dual-Bed Catalyst Systems - Start engine. After engine is warmed up, check for air supply to catalyst by removing the hose connecting diverter valve to catalyst.

If Air Supply to Catalyst System OK

If no Air Supply to Catalyst Check for air supply from pump outlet to exhaust manifold.

Test Response Probable Cause Action

No Air from Pump Pump Failure Replace Pump Loose Drive belt Tighten Leaks in the hose Replace hose or

hose fitting

Air supply to exhaust Vacuum present at Check vacuum hose manifold switch valve routings. Check

computer.*

Switch valve Replace valve inoperative

Air dumped to air Diverter valve Check computer* cleaner/atmosphere inoperative Replace diverter valve

Heat damage to hoses Check valve Replace check valve and air pump inoperative

Backfire during Diverter valve Replace diverter valve deceleration inoperative

*See "closed-loop" system performance check.

4-9

TABLE 4-4 (cont'd)

Performance Test (continued)

(2) Single-Bed Catalyst System - Start engine. After engine is warmed up, check for air supply to air cleaner or atmosphere.

If air supply to catalyst System not OK If air supply to atmosphere System OK

Test Response Probable Cause Action

Air supply to Vacuum present at Check vacuum hose exhaust manifold switch valve routings. Check or catalyst temperature sensor*

No air from pump Pump failure Replace pump. Loose drive belt Tighten belts. Leaks in the hose Replace hose or

or hose fittings or hose fittings.

Heat damage to hoses Check valve Replace check valve and/or air pump inoperative

Backfire during Diverter valve Replace diverter deceleration inoperative

PULSE AIR SYSTEM

Performance Test - With engine running, check for hissing noise near

pulse air valve. Turn off engine. See if rubber hose or air valve

exhibits heat damage. Apply a vacuum to the rubber hose connecting

pulse air valve to air cleaner. Valve should hold vacuum for 2 seconds.

Replace valve if there are signs of heat damage or it does not hold

vacuum for 2 seconds.

*See closed-loop system performance check

4-10

DUAL BED CATALYTIC COWERTER

_____.,____-+-_, REDUCING ...._____

.;::~~--~ CATALYST __,...__ --.

i OXIDIZING CATALYST

FIGURE 4-1

SCHEMATIC OF SECONDARY AIR SYSTEi'l (Example)

FUEL CONTROL DUAL BED CATALYTIC CONVERTER

----------+--' REDUCING ..__ __.'P.!~------------:~2;....._--1~ CATALYST.--.....---.

SENSOR

ALVE

OXIDIZING CATALYST

• CHECK VALVE IA SWITCHING VALVE

ELECTRICAL SIGNALS FROM ECM

AIR CONTROL VALVE •

BY-PASS AIR TO AIR CLEANER • 1\\0 -VALVES OR INTEGRAL

(a) Cold-Start

~~t-----1 EC M

FUEL CONTROL

'-----------0

SENSOR

CHECK VALVE

..·.·,·.·.·.·.•.•,•.•.•,•.·.·.·.············-·.·.•.·.•.·.·.·.·.·.•.··.···········································

ELECTRICAL SIGNALS FROM ECMAIR PUM

AIR SWITCHING VALVE•

.•.·.•.·,•,•··············

-- AIR CONTROL VALVE •

BY·PASS AIR TO AIR CLEANER • TI\O - VALVES OR INTEGRAL SOURCE: GM (b) Engine Warmed-Up

4-11

Table 4-5 provides the diagnostic procedures for EGR systems. Care was

taken to distinguish between backpressure and ported vacuum systems and

an example schematic of each type of system is shown in Figure 4-2. As

for secondary air systems, the diagnostics were derived from manufacturer

recommendations. The procedure consists of a simple functional check to

see if the valve is working and a series of additional checks to trace

the fault to the vacuum signal source or to the EGR valve itself.

The major effort in the contract was towards development of standardized

procedure for the relatively complex closed-loop fuel system. Based on

an ingenious test developed by Chrysler, EEA first developed a closed

loop system performance check that is applicable to all vehicles regard

less of whether the system utilizes a feedback carburetor or fuel injec

tion. This is detailed in Table 4-6.

The closed-loop system performance check provides a quick and easy check

on the central aspect of closed-loop control -- the control of air-fuel

mixture to the catalyst at stoichiometry. If this check is positive, it

can be stated that all of the significant components in the closed-loop

system are working correctly when the engine is warmed-up. Essentially,

the performance check utilizes the human body as a surrogate oxygen sensor

and alternately grounding and touching the positive terminal of the battery

causes the computer to switch between rich and lean alternately. This

results in an audible increase or decrease in engine RPM (from fast idle)

if the system is operational. Additional checks with a CO meter can

verify if the air-fuel ratio actually oscillates about stoichiometry

since CO emissions rise rapidly if the engine is slightly richer than

stoichiometric. EEA has performed an engineering test of the closed-

loop system check on a variety of cars and the results are tabulated in

Table 4-7. As can be seen from the results, the system performance check

can be implemented on any closed-loop car and the results can be monitored

accurately.

4-12

TABLE 4-5

DIAGNOSIS OF EGR SYSTEMS (Backpressure and Ported Vacuum System)

System Performance Check: With engine off, place finger under EGR valve

and push on diaphragm. EGR valve should move freely from open to close

(or replace EGR valve). With transmission in "Park" or "Neutral" and

engine running, open throttle to increase engine rpm to 2000. EGR

diaphragm should move up (valve open). (Caution: with backpressure

EGR, exhaust must be blocked partially to create enough backpressure for

EGR to open.) Close throttle on engine and EGR valve should close.

Test Response Probable Cause Action

EGR valve not open

does Vacuum hoses connected or

improperly leaking

Check and replace hose.

Defective EGR valve Connect external vacuum to EGR valve. With engine at fast idle apply vacuum to valve. If valve does not open, place.

re

Valve does on system check, with external

not open opens

vacuum.

Defective thermal switch (TVS)*

vacuum Disconnect TVS and bypass it. If EGR valve opens, replace TVS.

Defective control system plugged vacuum passage

Check EGR vacuum at carburetor or manifold. Clean Vacuum passages.

*In some cars, the EGR vacuum is controlled by an electrical solenoid that is turned on by the computer. If solenoid is inoperative, replace or else check computer (Table 4-6).

4-13

TABLE 4-5 (cont'd)

Test Response

Valve does not stay open with external vacuum (Ported vacuum system only)

EGR valve open at idle

Engine rough at idle EGR valve closed

Probable Cause

Defective or leaking diaphragm

Vacuum control defective

High EGR leakage with valve closed

Action

Apply vacuum and clamp hose. Valve should remain open for at lease 30 seconds, or replace.

Disconnect vacuum hose from valve. If valve closes, check carburetor for sticking throttle. If valve opens, replace EGR valve.

Remove EGR valve and inspect to ensure poppet is seated. Clean deposits, if necessary or replace.

4-14

FIGURE 4-2

SCHEMATIC OF EGR SYSTEMS (Example)

Type-I Ported Vacuum Air

Throttle chamber

,' .Jr Throttle valve

Exhaust gas from exhaust manifold

,~I

Engine coolant

E.G.R. Vacuum control :rort

Intake manifold

Type-2 Back Pressure Air

~